This invention relates to a double-chamber tank which is capable of separately accommodating gasoline and lubricating oil for instance, and hence suited for use in a portable power working machine. This invention also relates to a method of manufacturing such a double-chamber tank.
In the case of a portable power working machine such as a chain saw, a bush cutter, etc., not only gasoline but also lubricating oil is required to be supplied to an air-cooled two-stroke gasoline internal combustion engine mounted as a power source on the working machine since the engine needs lubricating oil in a separate oiling system or the working portion of the chain saw individually needs lubricating oil. In order to meet such requirements, there has been proposed, as set forth in Japanese Utility Model Publication H/6-21297 and in Japanese Utility Model Unexamined Publication H/6-60737, an idea wherein a tank for gasoline and a tank for lubricating oil are separately produced at first and then subsequently combined so as to be attached to a main body of the working machine by means of a strap, etc.
The aforementioned idea of separately preparing two tanks and subsequently combining them is however accompanied with problems that since two tanks are required to be separately produced, it leads not only to an increase in total manufacturing cost thereof, but also to the consumption of time in assembling as well as mounting them.
Further, a closed type tank whose upper surface is closed such as shown in the aforementioned publications is frequently manufactured by means of a blow molding method. However, the blow molding method is accompanied with problems that a strict weight control of molding material is required, and that even if a molding material is strictly controlled in weight thereof, uneveness in thickness of the molded product tends to be generated so that the external appearance of the molded product is not so good. Furthermore, after the blow molding of these two tanks, a drilling operation of these two tanks for forming an inlet port for pouring fluid such as gasoline, lubricating oil, etc., or for forming fixing portions thereof is required to be performed thus increasing manufacturing steps before these tanks are finally accomplished.
When it is required to accommodate two kinds of fluid in a limited space as in the case of the aforementioned portable power working machine, it may be conceivable to provide the working machine with a double-chamber tank comprising two closed type tanks which are integrated with each other, i.e. a closed type double-chamber tank comprising two tanks, one for accommodating gasoline and the other for accommodating lubricating oil. However, it has been very difficult to manufacture a double-chamber tank of this kind by means of blow molding method, so that no one has succeeded up to date to provide a double-chamber tank which is capable of overcoming the aforementioned problems.